One type of buccal hygiene apparatus includes a casing enclosing a hydraulic pump and motor unit. A handpiece is connected to the casing by a flexible tubing. A reservoir is removably fittable on the casing in a position for supplying water to the pump and motor unit via an outlet in the bottom of the reservoir. The outlet has a valve for closing it when the reservoir is fitted on the casing.
In that type of apparatus, the handpiece can receive a spray head which delivers a jet of pulsated water for cleaning the teeth and massaging the gums. In some "combined" apparatus, the spray nozzle can be replaced by a toothbrush which is oscillated by a hydraulic motor housed in the handpiece. In both of these conventional types of devices, the reservoir supplies water to the pump and motor unit independent of the water supply.
In general, the reservoir is provided to perform a dual purpose, as a water-supply reservoir and, when emptied of water and turned up the other way, as a cover or lid for the apparatus when it is not in use. Because of this fact, the conventional reservoirs must be sufficiently large to fit on and cover the housing.
This feature often proves to be a disadvantage due to the relatively large dimensions of the reservoir which make it clumsy to handle for the purpose of filling the water and, when it is filled with water, it is not always easy to correctly fit it, the first time, on the housing with its outlet coinciding with the pump inlet. These disadvantages become particularly noticeable when the apparatus is used by children when they experience difficulty in holding the reservoir in one hand. The reservoir may thus be held in both hands, or by its upper rim, with a thumb extending into the reservoir, and this in unhygienic.